Gravity-fed watering devices have been used for a number of years in order to provide water for livestock, such as chickens, to drink. In general, the watering device includes a basin having a low wall that defines a drinking trough. A metal or plastic water reservoir is mounted above the basin.
In use, the reservoir is positioned on the basin such that an open end is downwardly-oriented, akin to a bucket that is turned upside down. In order to fill the watering device, the reservoir is detached from the basin. The reservoir is then inverted so that its open end is exposed. Water may then be filled into the reservoir, which then retains the water. After the reservoir is filled, the basin is reattached to the reservoir, and the device is tipped over, such that the basin is upwardly-oriented and the reservoir is downwardly-oriented. In this orientation, the outer circumferential wall of the basin overhangs the reservoir, as the diameter of the basin exceeds that of the reservoir.
FIG. 1 illustrates a cross-sectional view of a conventional watering device 10. The device 10 includes a basin 12 having a base 14 integrally formed with an outer wall 16 defining a water-retaining volume therebetween. The device 10 also includes a reservoir 18 having a base 20 integrally formed with circumferential walls 22. An open end of the reservoir leads to a cavity 24 configured to receive and retain water 26.
As shown in FIG. 1, the device 10 is in an operational configuration such that the reservoir 18 is attached to the basin 12. As noted above, the outer wall 16 of the basin 12 overhangs an outer circumference of the reservoir 18.
The edges of the walls 22 of the reservoir 18 attach to the basin 12 at a level that is lower than the upper edges of the outer wall 16 of the basin 12. Accordingly, a drinking trough 28 is defined between the outer wall 16 and the edges of the walls 22.
A channel or notch may be formed proximate the edge of the walls 22 of the reservoir 18. The channel allows water to flow by force of gravity from the reservoir 18 into the trough 28. As water flows out of the reservoir 18, it is replaced by air that bubbles past the edge and collects in a space 29 above the water 26 contained within the reservoir 18.
As the water level in the trough 28 rises, however, the edge of the reservoir 18 becomes submerged, and backward flow of air into the reservoir 18 stops. At this point, water continues to flow, thereby expanding the volume of the space 29 trapped inside the reservoir 18. However, because air is no longer flowing into the volume of the space 29, air pressure therein decreases. Water continues to flow from the reservoir 18 into the trough 28 until the weight of the water 26 inside the reservoir 18 plus the pressure of the trapped air is balanced by ambient air pressure outside the reservoir 18.
The flow of water from the reservoir 18 into the trough continues to rise until it reaches the lower edge of the reservoir 18. At this point, the water seals off the path that previously allowed air to enter. As water then continues to flow from the reservoir 18, it is not replaced by air, but, instead, a partial vacuum is formed above the water in the space 29. Water continues to flow until the pressure from the water and air inside the reservoir 18 equals the pressure from the water and air outside the reservoir 18, as described in the following equation:pr+pwr=pd+pwd where pr is the air pressure above the water inside the reservoir 18, pwr is the water pressure inside the reservoir 18, pd is the air pressure above the drinking trough 28, and pwd is the water pressure in the drinking trough 28.
The water pressures may also be represented by ρAh, where ρ is the water density, A is a unit area, and h is the height of the water. Therefore, using the above equation:pr+ρAhwr=pd+ρAhwd 
From this equation, it is seen that as a volume of reduced air pressure pr forms in the reservoir, the height hwr of water supported in the reservoir 18 can be significantly larger than the height hwd of water in the drinking trough 28. For a typical poultry watering device with a reservoir 15 inches tall, this equilibrium state occurs when the water in the drinking tough has risen less than 0.1 inches above the point where it prevents air from entering the reservoir.
The key to this operation is that the reservoir 18 is air tight. If, for example, a leak was to develop in the reservoir 18 which allowed air to enter, the air pressure inside the reservoir 18 would equal the air pressure outside the reservoir 18, so, using the equation above, pr=pd. Thus, all the water would run out of the reservoir 18 until hwr=hwd. By maintaining an air-tight reservoir 18, water is retained therein. Then, as chickens consume water in the drinking trough 28, the water level drops until the edge of the reservoir 18 is exposed. Air can then enter the reservoir 18, thereby allowing more water to flow into the trough 28 which, in turn, again submerges the edge of the reservoir 18 to stop the process. While this method of providing water is simple and efficient, it is not conducive for replenishing water within the reservoir 18.
As discussed above, the reservoir 18 is typically detached and inverted for filling. Then the basin 12 is reattached to the reservoir 18, and the entire device 10 is turned right-side-up, spilling water in the process.
Some devices, however, maintain connection between the basin and the reservoir at all times and fill through a valve in the basin. However, such devices still must be turned back over after filling, resulting in spillage.
To alleviate these drawbacks, certain devices have been configured to allow for filling of the reservoir from the top. A typical top-filling device includes a reservoir in the shape of a jug or tank having an air-tight lid and a small hole in the bottom of the jug to allow water to flow into the drinking trough.
FIG. 2 illustrates a cross-sectional view of a conventional top-filling watering device 30. The device 30 includes a jug or tank 32 positioned within a basin 34. The tank 32 includes an opening 36 near its bottom that allows water to flow from the tank 32 into the basin 34. In order to re-fill the tank 32, an air-tight lid 38 is removed. For example, the lid 38 may be unscrewed from the top of the tank 32. Before the lid 38 is unscrewed, however, a small cover or cap is placed over the opening 36. The lid 38 is then removed and the tank 32 is filled with water. Once re-filled to a desired level, the lid 38 is securely replaced on the tank 32, and the cover or cap is removed from the opening 36.
Thus, in order to fill the tank 32, there are a number of distinct steps. First, the small cover or cap is located and then positioned on or in the opening 36. The lid 38 is then removed from the tank 32. Water is then poured into the tank 32. After water is poured to a desired level, the lid 38 is secured back on the tank 32. The cap or cover on the opening 36 is then removed. Moreover, during this process, a user typically sticks his/her fingers into the drinking trough to either cover or uncover the opening 36 before and after filling.
Additionally, the lid 38 typically includes a gasket or O-ring configured to seal around an inlet neck of the tank 32. However, over time, the gasket or O-ring typically dries out and leaks. Continual opening and closing of the lid 38 wears on the gaskets and contributes to leaks. Such leaks may cause water to overflow from the tank 32 into the basin 34.
Further, during the filling process, the lid 38 is completely removed from the tank 32. In general, however, a typical livestock area, such as a poultry barn, does not generally, include many clean areas in which to set the lid 38. Therefore, an operator generally holds onto the lid 38 or risks getting it dirty, which could contaminate the drinking water.
Also, because the tank 32 is formed as a large jug-like structure, it is not amenable to nesting with other tanks during shipping. Accordingly, shipping costs for typical top-filling watering devices are generally higher than other watering devices, such as shown in FIG. 1.